Refining of vegetable oils



May 13, 1941- B. H. THURMAN 242,188

REFINING OF VEGETABLE OILS Filed Aug. 30, 1940 Patented May 13, 1941 s REFINING 2,242,188 or` VEGETABLE olLs Benjamin H. Thurman, Bronxviile, N. Y., assignor to Refining, Inc., Reno, Nev., a corporation' of Nevada applic-atan August 3o, 1940, serial N. 354,888

claims. (ci. 26o-,425)

Thsinvention relates Vto the `refining of ,vegetable oils, and more particularly to a process of partial rening in'which gummy material carried by the oils is removed prior to complete refining, although the gum liquefyingl agents vdis- ,closed herewith may also be employed in com-- plete refining processes to decreasev the entrainment of oil in foots separated therefrom so as to decrease refining losses.

The invention is particularly applicable to socalled degumming processes in which gummy materials such as phosphatides', proteins, resins and carbohydrates are removed from the oil prior to an alkali refining step. -In such separations the gummy material referred to is precipitated fromthe oil and then separated therefrom by 'a difference in speciiic gravity. 'I'his material is a valuable by-product either as a phosphatidic material as separated or as a source of valuable phosphatides and other materials. A considerable amount of oil is ordinarily entrained Withthe separated gums,

process in which entrainment of.l neutral oil in 4 the soap stock isreduced. V

'I'he process of the present invention is preferably carried out as a continuousv operation in a closed system', although markedl improvement over` conventional batch operations is accomplished. in accordance with the present invention even in batch operations. The invention will be specifically described with reference to the accompanying drawing, which is a schematic diagram of an apparatus suitable fori carrying out a continuous degummingoperation in accordance with the present invention.

Referring to the drawing, I0 indicates a tank or other source of supply of crude vegetable oil; II indicates a source of supply for an anti-sticking agent, and I2 indicates a source of supply of a gum liquefying agent. In the preferred opera@ tion, a stream of crude oil is withdrawn'fromthe tank I0 byI a proportoning pump Il and forced through a heat exchange device I4 to a mixing device It. The heating device Il preferably inand represents a major rening loss. Itis difficult to recover the oil entrained with the gums,

and the present invention is directed to minimizing the amount of this oil.

It is, therefore, an object ofthe present in,-

vention to provide an improved process of removing gums from vegetable oils. l i

f" Another object of the'invention istoy provide inwhich a gum liquefying agent is employed to enable more complete separation oi' o il froml the gums. l y A further object of theinvention is to provide y a process of removing gumsirom vegetable oil f arated gums from stickingto the walls of the centrifugal bowl." s i The Vgum liquefying agent is` also advantageously employed incomplete alkali rening operations, in which sufficient alkali is added lto `the crude oil in amounts and, concentrations known to the ar't to completely neutralize the free fatty acids therein `as well as to reduce co1- ors in -highlylcolored oils. In such, operations the gums are present in the soap stock separated from the oil, and the gumliquefying agent improves the separation so as to reduce entrainmentof neutral oil with the soap stock.

It is therefore a still further object of the inventionv to Aprovide an improved alkali refining cludes a heating coil I5 positioned in a vcasing I1 through which any desired heating or cooling medium may be circulated. Anti-sticking agent i is withdrawn from the tank Il by means-of a proportioning 4pump I8 and delivered v to the mixing device I5. The crude oil and anti-sticking agentiare thoroughly admixed in the, mixer I5 which is preferably of thetype disclosed in my copending application Serial No. 190,673filed` February 15, 1938, now Patent No. 2,142,062, granted Sept. 29, 1938, but 'which may be any type of closed iiow mixer such as a closedme chanical agitator. Themixture from the mixing device I5 is preferably delivered to a second mixing device- I9, which may be of the same type asthe mixing device 'I5. Gum liquefying agent is withdrawnA from the tank I2. by a'proportioning pump .20 and delivered to` the mixer I9. lThe proportioning pumps I3, I8 and 20`maybe driven by a variable speedelectric motor 2l with variable speed devices 22 and23 between the motor and the pumps Il and 20. This proportioning mechanism is given 'merely as an example, as

anysuitable proportioning mechanism capable of accurately proportioning ystreams under pump pressurecan be employed. The resulting mix'- ture from the mixer I9 is then preferably passed through a second' heat exchange device 2 4in- -cluding a heating coil 25 positioned in a casing 26 through which any desired heating or cooling medium`may be passed. Both the litluetyin'gy agent and anti-sticking agent are"preierably-` aqueous solutions and leither or'. both act as gum precipitating agents to render the gums insoluble in the oil and capable of being separated therefrom as foots.

'I'he resulting mixture of oil and foots is then delivered to a continuous centrifugal separator 2l which is preferably of the heated type disclosed in Patent No. 2,100,277, granted November 23, 1937. The precipitated gums or foots are separated from the oil in the centrifugal 21 and delivered as the heavy effluent through a spout 28 into a receiver 29. The degummed oil is delivered as the light effluent through a spout I into a receiver 3i.

Substantially all vegetable oils contain gummy materials such as above described which must be removed in order to produce a commercial refined oil. The gums are preferably removed priorv to the removal of free fatty acids, also contained in the oil, although both the gums and fatty acids may be removed in the same operation. Examples of vegetable oils which may be treated by the present invention are cottonseed oil, soya bean oil, sesame oil, corn oil, rapeseed oil, etc. The gums are to a large extent soluble in the oil, but may be rendered to a large extent insoluble therein by the addition of water to the oil. The addition of water alone, however, does not precipitate all of the gums, and the resulting mix ture of precipitated gums and oil is difllcult to separate without leaving large amounts of oil admixed with the gums. It hasbeen found that solutions of weak acid, for example, boric acid, tartaric acid, citric acid, etc., as well as extremely dilute solutions of strong acids such as sulfuric or hydrochloric acid, accomplish a more complete precipitation of the gums and the same is true of relatively dilute solutions of neutral salts such as sodium chloride or sodium sulfate and also relatively dilute solutions of weakV alkalies or very dilute solutions of strong alkalies. Although the gums are more completely precipitated by such degumming reagents, the separated gums are quite viscous and are excellent emulsifying agents, so that they entrain considerable valuable oil.

In accordance with the present invention, I

have found that certain agents appear to render the gums more liquid in nature, thereby enabling a more complete separation to be made. These agents also decrease the emulsifying action of the gums. In general water soluble salts such as salts of alkali metals or alkaline earth metals, y

ammonium salts, etc., other than alkali metal halides or stronglyalkaline salts are suitable as gum liquifying agents in the present invention. The term strongly alkaline salts is employed herein to mean salts which are sufficiently alkaline in reaction to react readily with free fatty acids. Certain salts of alkalies for example sodium carbonate and tri-sodium phosphate come within this term and function as alkaline refining reagents, as is known by those skilled in the art of vegetable oil refining. The halides of alkali metals, for example, sodium chloride, have a hardening effect upon the gums instead of a gum softening or liquefying action.

The preferred liquefying agent is sodium thiosulfate, which, when added in relatively small amounts and concentration, causes a much more complete separation of the gums from the oil. Other thiosalts are also very eective, for example. sodium thiocyanate and other alkali thiosulfates and thiocyanates such as ammonium and potassium thiosulfates and thiocyanates. These materials, particularly the sodium thiosulfate. also produce a greater precipitation of the gums.

so that the other reagents, namely, the acid alkaline or neutral salt solutions, are not essential for good precipitation, but may be employed in admixture therewith, if desired. However, other water soluble salts, such as calcium chloride, ammonium chloride, ammonium acetate, calcium thiocyanate, magnesium sulfate, potassium tartrate, potassium sulfate, sodium sulfate, barium chloride, etc. may also be employed. It will be apparent that the extent of gum liquefying will depend upon the water soluble salt selected and also that care must be exercised in employing such gum liquefying agents in admixture with acid or alkaline refining reagents or alkaline antisticking agents to avoid precipitating insoluble compounds from reactions between the refining or anti-sticking reagent and the gum liquefying agent. For example, insoluble alkaline earth metal hydroxides or carbonates will precipitate if water soluble alkaline earth metal salts are employed with refining agents comprising alkali metal hydroxides or carbonates and insoluble sulfates will precipitate if water soluble barium of calcium salts are employed with sulfuric acid as a refining agent. yAlso, mixtures of'water soluble salts may be employed as gum liquefying agents if such insoluble, precipitates are not formed. The amount and concentration of the gum liquefying agent will vary with the nature of the oil and the amount of gums contained therein. Thus, a concentration of from 1 to 20% in amounts of from l to 15% based on the weight of the oil may be employed. In ordinary operations, 10% solutions of the gum liquefying agent can ordinarily be employed in amounts ranging from 1 to 5%.

Although the `gum liquefying reagents referred to produce a much cleaner separation of the oil from the foots, it is found in some cases that portions of the gummy materials adhere to the walls of a centrifugal bowl so as to build up a layer of gummy material interfering with proper separation in continued operations. The most effective means of preventing this is to add to the oil a small percentage of a relatively dilute solution of a strong alkali prior to adding the gum liquefying agent. Such alkalies neutralize a small portion of the free fatty acids of the oils to form a small amount of soap. This soap apparently acts as a lubricant or slipping agent for the gums in the centrifugal bowl and prevents adherence thereof.

"Thus, from .1 to 5% of 12 B. caustic soda has been found particularly effective, although other alkalies may be employed. It has been consistently noted that the addition oi' small amounts of alkalisuchas above described not only cause the foots to i'low continuously from the centrifuge without building up a layer of gummy material' but also reduce the fatty acid content of the oil to a greater extent than would be expected from i the amount of alkali employed. The soap formed from the alkali appears to be the primary factor in preventing the building up ot a layer in the centrifugal separator. Buch soap is preferably formed in situ, as above described, but can be added in solution as a separate material. Also, it has been found that other materials. such as small amounts of starch or dextrin solutions, will accomplish a somewhat similar result.

The centrifugal separating operation is most effective at somewhat elevated temperatures, for example, temperatures between and 160 F. depending upon the nature of the oils and the amount of gums contained therein. The ele'- vated temperatures further reduce the vlscosities of the oil and gums and help to break any liquefy gums contained in said ioots in order to reduce the oil entrained with the `foots after separation.

3. The process of refining vegetable oils con-y ciiic gravity, whereby the amount oi' oil en-v trained in said roots is minimized.

4l. The process of reilning vegetable `oils containing gums, which comprisesmixing a stream oi a refining reagent which reacts with impurities in said oil to .precipitate roots with a. iowing stream of said oil, incorporating a gum liquefying agent comprising a water soluble salt other than alkali metal halides or strongly alkaline salts with said mixture in order to liquefy gums contained in said roots and continuously centriiugally separating said foots i'rom said oil vbl? dierence in specific gravity in order to minimize the amount oi oil entrained in said foots.

5. The process of rening vegetable oils containing gums, which comprises, mixing astream of a refining reagent .which reactswith impurities in said o'il to precipitate roots with a owing stream of said oil, incorporating an aqueous solution of a water soluble salt other than alkali metal halides and strongly alkaline salts with said mixture in order to liquefy gums contained in said foots, and continuously centriiugally sep'-` arating said foots from said oil, whereby the amount of oil entrained in said ioots is minimized 6. The process of partially refining crude. vege table oils containing gums and free fatty acids,

which comprises, mixing an alkali reiining re` agent with said oil to precipitate said gums but inan amount insufiicient to neutralize all of the free fatty acids o! said oil, also adding angaqueous solution of a water soluble salt other than the alkali metal halides and strongly alkaline salts with said oil to assist in precipitating said gums and to reduce the viscosity thereof, thereafter separating said gums from said oil by continuous centrifugal separation, whereby said gums ilow continuously from the centrifugal separator employed and contain a reduced amount of entrained oil. l

7. 'Ihe process of partially reilning vegetable oils containing gums, which comprises, mixing a gum precipitating and liquefying reagent comprising a water soluble salt other than an alkali metal halide and a strongly alkaline saltwith said oil to precipitate gums having a reduced viscosity, and thereafter centrifugally separating the precipitated gums from said oil, whereby the oil entrained in said gums is reduced. 8. 'I'he process oi' partially reiiningvegetable oils containing gums, which comprises, mixing an aqueous solution of soluble alkali' thiosulfate with said oil to precipitate gums having a reduced viscosity, and thereafter separating the precipitated gums from said oil, whereby the oily entrained with said is reduced.

9. In the process of refining vegetable oils containing gums, which includes the steps of adding a reilning reagent to a vegetable oil and separatingthe resulting roots by diil'erence in speciilc gravity, the improvement which comprises, incorporating sodium thiosuliate with the mixture of oil and ioots resulting from adding said refining reagent to said oil. so as tol liqueiy gums contained in said i'oots in order to reduce the oil entrained with the foots after separation.

10. In the. process of refining vegetable oils containing gums, which includes ,the stepsoi! mixing a reilning reagent with an oil in` order to form a mixture o! oil and i'oots including gums and separating said roots from said oil, the improvement which comprises incorporating sodium thiosulfate with said` mixture in order to reducethe amount of oil entrained with the separated foots. f f

1l. The process of refining vegetable oils containinggums, which comprises. mixing a relinng reagent with said oil which reacts with impurities in said oil to precipitate foots, adding an aqueous solution oi' sodiumthiosulfate to said oil prior tomixing `said reilning reagent therewithin order to liqueiy gums contained in said foots, and separating said i'oots from said oil by difference in specinc` gravity, y whereby the amount of oil entrainedl in said i'oots is minimized. f A

12. The process of refining vegetable oils containing gums. which comprises, mixing a stream oi! a reilning reagent which reacts with impurities in saidoil to precipitate foots with a ilowinil stream oi' said oil, incorporating sodium thiosulfate with said mixture in order to liquefy gums contained in said foots, and continuously centrifugally separating said foot; from said oil, whereby the amount ci oil entrained in said foots isminimired. v

Y 13. The process ot partially `reilning crude vegetable oils containing gums and free fatty acids, which comprises, mixing an alkali renning reagent with said oil to precipitate said gums butin an amount insumcientto `neutralize all of the tree fatty acidsoi said oil, also adding` an aqueous solution of sodium thiosuliate with said oil to assist in precipitating said gums and to reduce the viscosity thereof, thereafter lsepa-rat-` ing said gums from said oil by continuous centrii'ugal separation, whereby said gums ilow oontinuously from the centrifugal separator employed andcontain s reduced amount of entrained oil. n A i 14. The process of partially refining vegetable oils containing gums, which comprises, mixing an aqueous solution of sodium thiosultate with 4said oilsto precipitate gums having a reduced BENJAMIN H. THURMAN.

CERTIFICATE CF CORRECTION.

Patent No. 2,2LI2,188. f. t may 15, 19in.

BENJAMIN H. THURMAN, Y It is herebycertfied lthat error appears in the' printed specification of the abete numbered patent. requiring correction as follews: Page 2, second column, line 51, for' "5% read '.5"{; endfth'atthe seid Letters Petent should be'read .with this correction'therekinfftht lthe Same conform l to the record of the case in thePatent-Iofrie; l e

signed and sealed this 17th day-of JunegA; D. 19m. C

I Henry Van Arsdale, (Seal) C Acting Conmssoner of Patents.' 

